Forwarding Messages Within a Switch Fabric of an Sdn Switch

1. A Software-Defined Networking (SDN) switch comprising: a first plurality of external network ports for receiving external network traffic onto the SDN switch; a second plurality of external network ports for transmitting external network traffic out of the SDN switch; a first Network Flow Switch (NFX) integrated circuit that has a plurality of network ports and that maintains a first flow table, wherein a first network port of the first NFX integrated circuit is coupled to a first of the first plurality of external network ports, and wherein a second of the network ports of the first NFX integrated circuit is coupled to a first of the second plurality of external network ports; a second Network Flow Switch (NFX) integrated circuit that has a plurality of network ports and that maintains a second flow table, wherein a first network port of the second NFX integrated circuit is coupled to a second of the first plurality of external network ports, wherein a second of the network ports of the second NFX integrated circuit is coupled to a second of the second plurality of external network ports, and wherein a third of the network ports of the second NFX integrated circuit is coupled to a third of the network ports of the first NFX integrated circuit; and a Network Flow Processor (NFP) circuit that maintains a third flow table, wherein the NFP circuit couples directly to a fourth of the network ports of the first NFX integrated circuit but does not couple directly to any network port of the second NFX integrated circuit, wherein the NFP circuit sends a flow entry to the first NFX integrated circuit along with an addressing label, wherein the first NFX integrated circuit receives the flow entry and addressing label and uses the addressing label to determine that the flow entry is to be forwarded to the second NFX integrated circuit, wherein the first NFX integrated circuit forwards the flow entry to the second NFX integrated circuit without the addressing label.

2. The SDN switch of claim 1 , wherein the second NFX integrated circuit receives the flow entry from the first NFX integrated circuit and loads the flow entry into the second flow table.

3. The SDN switch of claim 1 , wherein the flow entry and the addressing label are sent out of the NFP circuit as a part of a first MAC frame, wherein the first MAC frame has a MAC header, and wherein the flow entry is sent out of the first NFX integrated circuit as part of a second MAC frame, wherein the second MAC frame has a MAC header.

4. The SDN switch of claim 1 , wherein the NFP circuit does not execute a SDN protocol stack, and wherein neither the first nor the second NFX integrated circuits executes an SDN protocol stack.

5. The SDN switch of claim 4 , further comprising: a controller processor circuit that is coupled to the NFP circuit via a serial bus, wherein the controller processor circuit executes a SDN protocol stack and maintains a fourth flow table, wherein the fourth flow table stores SDN flow entries.

6. The SDN switch of claim 1 , further comprising: additional NFX integrated circuits, wherein the NFP circuit can cause a flow entry to be communicated from the NFP circuit and to a selected one of the additional NFX integrated circuits by causing the flow entry to be forwarded through one or more of the other NFX integrated circuits.

7. The SDN switch of claim 6 , wherein an NFX integrated circuit that forwards the flow entry removes one addressing label before forwarding the flow entry.

8. The SDN switch of claim 6 , wherein the NFP circuit is not directly coupled to any of the first plurality of external network ports and is not directly coupled to any of the second plurality of external network ports.

9. The SDN switch of claim 1 , wherein the SDN switch comprises a plurality of printed circuit boards and a housing, wherein the first and second NFX integrated circuits and the NFP circuit are disposed on the printed circuit boards and are disposed within the housing.

10. A method involving a Software-Defined Networking (SDN) switch, wherein the SDN switch comprises a plurality of Network Flow Switch (NFX) integrated circuits, a Network Flow Processor (NFP) circuit, and a controller processor, the method comprising: (a) maintaining a flow table on each NFX integrated circuit, wherein none of the NFX integrated circuits executes any SDN protocol stack; (b) maintaining a flow table on the NFP circuit, wherein the NFP circuit executes no SDN protocol stack; (c) maintaining a flow table on the controller processor, wherein the controller processor does execute an SDN protocol stack; (d) communicating a flow entry out of the NFP circuit along with an addressing label, wherein the flow entry of the addressing label are communicated as parts of a first MAC frame; (e) receiving the first MAC frame onto a first of the NFX integrated circuits and using the addressing label to determine that the flow entry is to be forwarded to another NFX integrated circuit; (f) communicating the flow entry out of the first NFX integrated circuit and to the other NFX integrated circuit without the addressing label, wherein the flow entry is communicated out of the first NFX integrated circuit as part of a second MAC frame; (g) loading the flow entry into a flow table of a selected one of the NFX integrated circuits after the flow entry was forwarded through one or more others of the NFX integrated circuits, wherein the NFP circuit outputs the flow entry along with one or more addressing labels so that the flow entry will be loaded into the flow table of a selected one of the NFX integrated circuits, wherein the selected one of the NFX integrated circuits that is loaded with the flow entry is determined by the NFP circuit; and (h) using the flow tables of the NFX integrated circuit to control how packet traffic received onto the SDN switch is output from the SDN switch.

11. The method of claim 10 , wherein a first of the NFX integrated circuits is directly coupled to a second of the NFX integrated circuits by a network link but is not directly coupled to the NFP circuit by any network link, and wherein the NFP circuit can cause a flow entry to be forwarded through the second NFX integrated circuit and to be loaded into the flow table of the first NFX integrated circuit.

12. The method of claim 10 , wherein the flow entry is not a flow entry that was received onto the SDN switch as a part of any SDN protocol message.

13. The method of claim 10 , wherein the NFP circuit generates the flow entry.

14. A method of communicating a flow entry within a Software-Defined Networking (SDN) switch, wherein the SDN switch comprises a fabric of Network Flow Switch (NFX) circuits and a Network Flow Processor (NFP) circuit, wherein none of the NFX circuits comprises any SDN protocol stack, the method comprising: (a) generating the flow entry in the NFP circuit, wherein the flow entry is not a flow entry that was received onto the SDN switch as a part of any SDN protocol message; (b) outputting the flow entry out of the NFP circuit along with an addressing label, wherein the flow entry and the addressing label are communicated as parts of a first MAC frame; (c) receiving the first MAC frame onto a first of the NFX circuits and using the addressing label to determine that the flow entry is to be forwarded to another NFX circuit; (d) communicating the flow entry out of the first NFX circuit and to the other NFX circuit without the addressing label, wherein the flow entry is communicated out of the first NFX circuit as part of a second MAC frame; (e) loading the flow entry into a flow table of a selected one of the NFX circuits after the flow entry was forwarded through one or more others of the NFX circuits, wherein the NFP circuit outputs the flow entry along with one or more addressing labels so that the flow entry will be loaded into the flow table of a selected one of the NFX circuits, wherein the selected one of the NFX circuits that is loaded with the flow entry is determined by the NFP circuit; (f) storing SDN flow entries in the SDN switch; and (g) receiving packets onto the SDN switch via the fabric of NFX integrated circuits and outputting the packets from the fabric of NFX integrated circuits in accordance with the SDN flow entries stored in the SDN switch.

15. The method of claim 14 , wherein none of the NFX circuits comprises any instruction-executing processor that fetches instructions, that has an instruction counter, and that analyzes packets.

16. The method of claim 14 , wherein the NFX circuits communicate packets to one another and to the NFP circuit via network links.

17. The method of claim 14 , wherein the SDN switch comprises a plurality of printed circuit boards and a housing, wherein the fabric of NFX circuits and the NFP circuit are disposed on the printed circuit boards and are disposed within the housing.

18. The method of claim 14 , wherein each of the NFX circuits comprises a flow table, the method further comprising: maintaining in the NFP circuit a copy of the flow table of each NFX circuit.

19. The method of claim 14 , further comprising: (h) communicating a command from the NFP circuit, through one or more NFX circuits, to a selected other one of the NFX circuits; and (i) in response to a receiving of the command onto the selected one of the NFX circuits deleting a selected flow entry from the flow table of the selected one of the NFX circuits.

20. The method of claim 14 , wherein each of the NFX circuits comprises a plurality of flow tables, the method further comprising: maintaining in the NFP circuit a copy of each of the flow tables of each NFX circuit, wherein each flow table directs the switching of a subset of the network ports in the NFX.